Ciguatoxins in sea fish: sophisticated testing strategy enables clarification of fish poisonings

BfR can reliably detect poisoning with ciguatoxins by combining different test methods

24-Mar-2022 - Germany

poisoning with ciguatoxins after consumption of a sea fish meal is still rare in Germany. However, ciguatera, as the disease is called, is one of the most frequent fish poisonings worldwide that do not have a bacterial origin. Against the background of the expansion of global trade in sea fish from all the world's oceans, an increase in ciguatera cases can therefore also be expected in Germany in the future. Repeated ciguatera outbreaks in Germany since 2012 prompted the National Reference Laboratory for the Monitoring of Marine biotoxins at the Federal Institute for Risk Assessment (BfR) to break new ground in detecting ciguatoxins in fish, even of unknown origin. "Our testing strategy is based on two methods," says scientist Dr. Dorina Bodi. "First, we use a highly sensitive cell culture test for screening, i.e. the rapid examination of even a larger number of samples of suspicious sea fish. This test selectively detects the toxic effect of the ciguatoxins. If it hits, the toxins are determined based on their chemical structure using modern, high-resolution instrumental analysis that couples liquid chromatography with mass spectrometry (LC-MS/MS)." The new testing strategy has been developed not only for testing fresh or frozen fish samples, but it is also suitable for prepared or dried fish. It proved successful in elucidating the causes of a ciguatera outbreak in 2017: Ciguatoxins were clearly detected in frozen raw fish from the same batch of fish.

In a research project, BfR scientists worked with the authorities of the affected German states to clarify in detail a ciguatera outbreak in Germany in 2017. Using the testing strategy, it was possible to prove that this outbreak was caused by two batches of misdeclared frozen fish caught in the western Pacific Ocean. Evidence of the presence of ciguatoxins was found by the U.S. Food and Drug Administration (FDA) in meal residues from prepared fish dishes consumed by the individuals who had contracted ciguatera. BfR detected ciguatoxins in samples of unprocessed fish from one of the affected batches.

When tracing the batches along the food chain, a comparison of the genetic material from the fish samples with the genetic material of fish species stored in a library (DNA barcoding) revealed that the fish species was Lutjanus bohar and not L. malabaricus as declared. It is known that the fish species L. bo har is susceptible to exposure to ciguatoxins depending on water temperature and certain weather events such as strong storms.

Ciguatoxins are produced by certain microalgae in tropical and subtropical waters of the world's oceans. Certain species of fish that feed on such algae ingest these harmful substances in their food and store them in internal organs and muscle flesh without these toxins affecting their organism. Since ciguatoxins are highly toxic to mammals, including humans, very small amounts in the nanogram range are sufficient to cause health disorders in the form of ciguatera.

The investigations of the 2017 ciguatera outbreak were conducted as part of a doctoral thesis at the National Reference Laboratory for the Monitoring of Marine Biotoxins in cooperation with the University of Naples. The findings obtained regarding the causative fish species underline the importance of food authenticity especially for food safety along global food chains.

As fish species from warmer sea regions are increasingly exported to the EU as frozen fillets, the investigation of ciguatoxins is of great importance for the clarification of poisoning cases. Ciguatoxin detection in combination with identification of the affected fish species can create awareness of ciguatoxin poisoning among the importer, institutions and consumers. On this basis, appropriate measures can be initiated to avoid the import of sea fish species with a high risk of containing ciguatoxins. The testing strategy applied by BfR in the study thus makes a decisive contribution to consumer protection.

Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.